Several processes are known for obtaining a nitrile from an aldoxime by the use of a dehydrating agent. Typical processes include: (A) a process where an aldoxime is allowed to react with an acid anhydride such as acetic anhydride for dehydration, and (B) a process where an aldoxime is dehydrated with a phosphonitrilic chloride trimer (hexachlorocyclotriphosphazene).
However, process (A) involves disadvantages of high cost of starting material because acetic anhydride is needed in an equimolar amount or more with respect to the amount of aldoxime, and in addition, disposal of waste acetic acid finally produced from the acetic anhydride is required. On the other hand, when process (B) is adopted, phosphonitrilic chloride must be used in an equimolar amount or more with respect to the amount of aldoxime, which means a high cost of starting material, and moreover, waste disposal is even more costly compared to the process utilizing acetic anhydride.
In order to avoid these disadvantages, a process utilizing an acid such as sulfuric acid as a dehydrating agent has been reported (Japanese patent publication kokoku No. 59144/1990). This process is superior to the above-mentioned process in respect of only a catalytic amount of acid and reduced amounts of wastes. But this process is still defective because of the limited application of the process. In detail, yield of 80% or more is assured to obtain a nitrile from an aromatic oxime, a reduced yield of 70% from an aliphatic oxime, and a very low yield of 12% from a terpene oxime, which indicates unsuitableness in the wide-range practice.
Accordingly, an object of this invention is to provide a process for producing a nitrile in high yields and at a remarkably advantageous production cost.